Dental vulcanizing-flask.



E. A. HEWES.

DENTAL VULCANIZING FLASK.

APPLICATION FILED APR. 14. 1915.

Patented Aug. 31, 1915.

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ERNEST ATHEL I-IEWES, 01 ESKBANK, DALKEITLET, SC GILAND.

Specification of Letters Patent. Patentad Aug, 31, 1915,

Application filed April 14, 1915. serial No. 21,292.

of Paris investment when heat is applied thereto or when the pressure at which vulcanization is eflected is suddenly reduced.

For the manufacture of dentures it is usual to form an investment of plaster of Paris which is cast around a waX model of the denture in a flask consisting of two complementary cup-shaped parts in each of which is formed one half of the investment. After the plaster of Paris has set, the waX model is softened by immersing the flask in hot water, and the model is removed from the investment. Unvulcanized rubber compound is then arranged in the mold which is heated for the purpose of rendering said compound plastic and facilitating the packing of the latter into the mold. The two parts of the flask are then assembled and tightly clamped together and the whole flask is then heated under pressure in a vulcanizer. During the preliminary heating of the flask there is considerable risk, unless the heat be applied gradually, of eruption of the investment from the flask due to the generation of steam near the bottom thereof more rapidly than it can escape upwardly through the plaster of Paris, and one of the objects of this invention is to prevent such eruption.

The above mentioned disadvantage in vulcanizing dentures is overcome in accordance with this invention by constructing one part of the flask with a perforated bottom and by providing a false bottom separable therefrom and adapted to cover or close saidperforations.

Referring to the accompanying drawings, Figure 1 is a plan of the lower part of a flask constructed according to this invention; Figs. 2 and 3 are cross sections on the lines 2-2 and 3-3, Fig. 1 respectively; and

F ig. 4 is an inverted plan showing the per-' forated and false bottoms.

As shown in the drawings, the bottom a of the lower part 'b of a vulcanizing flask is formed with series of perforations c and said said part Z) is provided with a false bottom d pivoted thereto by a pin 6. The side walls of the part b are undercut slightly as'at f, so that the investment (not shown) may be dovetailed into the flask.

Tn use during the preliminary heating of v the flask, the false bottom (Z is swung back and the perforations 0 being adjacent to the largest surface of the investment, permit of the ready escape of steam which is generated in the plaster of Paris of which the investment is formed and which passes therethrough to said perforations and thence out of the flask. v

When vulcanization is complete, the investment and the denture are in a softened condition and the false bottom d prevents the plaster from being blow through the perforations 0 if the vulcanizing pressure is suddenly reduced, and thus the risk of damage to the denture is avoided.

The false bottom d may be pivoted as shown, or it may be hinged, slidable, or otherwise separable from the perforated bottom a.

If desired, the upper part of the flask may be provided with perforated and false tops corresponding with the perforated and false bottoms a and d and be undercut so that part of the investment may be dovetailed therein.

What I claim is 1. A dental vulcanizing flask having two complementary cup-shaped parts, one of said parts having a perforated bottom and means adapted to close the perforations of tachably securing said parts together.

2. A dental vulcanizing flask having two complementary cup-shaped parts, one of said parts having a'perforated bottom and a false bottom separable therefrom and adapted to close the perforations of said perforated bottom, and means for detachably securing said parts together. V

3. A dental vulcanizing flask having two complementary cup-shaped parts, one of said p arts having undercut side walls, a perforated bottom and a false bottom pivoted to said part and separable therefrom and adapted to close the perforations of said perforated bottom. and means for detachably securing said parts together.

7 I p A dental vuioanizingflask having tWo 5 bottoms being pivoted to said parts and sep- Iarab1etherefromandadapted to .close the v perforations of said perforated bottoms,

and means for detachably securing said parts together.

ERNEST ATHEL HEWES.

Witnesses:

GEoReE JACK, LEWIS JOHN GAW.

: copie s of this patent may be obtained foriive cents each, by addressing the Commissioner of Patents, a Washington, D. O? 

